Clinical, serologic, and immunogenetic features of familial idiopathic inflammatory myopathy

Imputation of the major histocompatibility complex region identifies major independent variants associated with bullous pemphigoid and dermatomyositis in Han Chinese

As autoimmune skin diseases, both bullous pemphigoid (BP) and dermatomyositis (DM) show significant associations with the major histocompatibility complex (MHC) region. In fact, the coexistence of BP and DM has been previously reported. Therefore, we hypothesized that there may be a potential genetic correlation between BP and DM. Based on data for 312 BP patients, 128 DM patients, and 6793 healthy control subjects, in the MHC region, we imputed single-nucleotide polymorphisms (SNP), insertions and deletions (INDEL), and copy number variations (CNV) using the 1KGP phase 3 dataset and amino acids (AA) and SNP using a Han-MHC reference database. An association study revealed the most significant SNP associated with BP, namely, rs580921 (p = 1.06E-08, odds ratio [OR] = 1.61, 95% confidence interval [CI] = 1.37-1.90), which is located in the C6orf10 gene, and the most significant classic human leukocyte antigen (HLA) allele associated with DM, namely, HLA-DPB1*1701 (p = 6.56E-10, OR = 3.61, 95% CI = 2.40-5.42). Further stepwise regression analyses with rs580921 identified a threonine at position 163 of the HLA-B gene as a new independent disease-associated AA, and HLA-DPB1*1701 indicated that no loci were significant. Three-dimensional ribbon models revealed that the HLA-B AA position 163 (p = 3.93E-07, OR = 1.64, 95% CI = 1.35-1.98) located in the α2 domain of the HLA-B molecule was involved in the process of specific antigen presentation. The calculations showed that there was no significant genetic correlation between BP and DM. Our study identified three significant loci in the MHC region, proving that the HLA region was significantly correlated with BP and DM separately. Our research highlights the key role of the MHC region in disease susceptibility.

Familial aggregation and heritability: a nationwide family-based study of idiopathic inflammatory myopathies

OBJECTIVES

The magnitude of the genetic contribution to idiopathic inflammatory myopathies (IIMs) is unknown. In this project, we aimed to investigate the familial aggregation and heritability of IIM.

METHODS

This is a family-based study using nationwide healthcare register data in Sweden. We matched each patient with IIM to individuals without IIM, identified their first-degree relatives and determined the IIM status among all first-degree relatives. We estimated the adjusted ORs (aORs) of familial aggregation of IIM using conditional logistic regression. In addition, we used tetrachoric correlation to estimate the heritability of IIM.

RESULTS

We included 7615 first-degree relatives of 1620 patients with IIM diagnosed between 1997 and 2016 and 37 309 first-degree relatives of 7797 individuals without IIM. Compared with individuals without IIM, patients with IIM were more likely to have ≥1 first-degree relative affected by IIM (aOR=4.32, 95% CI 2.00 to 9.34). Furthermore, the aOR of familial aggregation of IIM in full siblings was 2.53 (95% CI 1.62 to 3.96). The heritability of IIM was 22% (95% CI 12% to 31%) among any first-degree relatives and 24% (95% CI 12% to 37%) among full siblings.

CONCLUSIONS

IIM has a familial component with a risk of aggregation among first-degree relatives and a heritability of about 20%. This information is of importance for future aetiological studies and in clinical counselling.

Risk factors and disease mechanisms in myositis

Autoimmune diseases develop as a result of chronic inflammation owing to interactions between genes and the environment. However, the mechanisms by which autoimmune diseases evolve remain poorly understood. Newly discovered risk factors and pathogenic processes in the various idiopathic inflammatory myopathy (IIM) phenotypes (known collectively as myositis) have illuminated innovative approaches for understanding these diseases. The HLA 8.1 ancestral haplotype is a key risk factor for major IIM phenotypes in some populations, and several genetic variants associated with other autoimmune diseases have been identified as IIM risk factors. Environmental risk factors are less well studied than genetic factors but might include viruses, bacteria, ultraviolet radiation, smoking, occupational and perinatal exposures and a growing list of drugs (including biologic agents) and dietary supplements. Disease mechanisms vary by phenotype, with evidence of shared innate and adaptive immune and metabolic pathways in some phenotypes but unique pathways in others. The heterogeneity and rarity of the IIMs make advancements in diagnosis and treatment cumbersome. Novel approaches, better-defined phenotypes, and international, multidisciplinary consensus have contributed to progress, and it is hoped that these methods will eventually enable therapeutic intervention before the onset or major progression of disease. In the future, preemptive strategies for IIM management might be possible.

A Path to Prediction of Outcomes in Juvenile Idiopathic Inflammatory Myopathy

Humans have an innate desire to observe and subsequently dissect an event into component pieces in an effort to better characterize the event. We then examine these pieces individually and in combinations using this information to determine the outcome of future similar events and the likelihood of their recurrence. Practically, this attempt to foretell an occurrence and predict its outcomes is evident in multiple disciplines ranging from meteorology to sociologic studies. In this manuscript we share the historical and present-day tools to predict course and outcome in juvenile idiopathic inflammatory myopathy including clinical features, testing, and biomarkers. Further we discuss considerations for building more complex predictive models of outcome especially in diseases such as juvenile idiopathic inflammatory myopathy where patients numbers are low. Many of the barriers to developing risk prediction models for juvenile idiopathic inflammatory myopathy outcomes have improved with many remaining challenges being addressed.

Dermatomyositis etiopathogenesis: a rebel soldier in the muscle

PURPOSE OF REVIEW

The purpose of this article is to review the etiopathogenesis of dermatomyositis, including the predisposing factors, triggers, inflammatory cells, pathways and target antigens associated with dermatomyositis.

RECENT FINDINGS

During the last few years, we have made considerable progress in unveiling the etiopathogenesis of dermatomyositis. In the first place, we have defined genes within the major histocompatibility complex locus as the greatest genetic risk factor for the disease. Second, we have demonstrated that certain environmental factors, as well as tumors, may trigger certain dermatomyositis subtypes. Moreover, we have established the importance of the interferon pathway in dermatomyositis pathogenesis compared with other myositis subtypes. But probably, the most remarkable advance has been the discovery of multiple autoantibodies that define groups of patients with characteristic clinical features, prognosis and response to treatment.

SUMMARY

Dermatomyositis cause and pathogenesis have proven to be a complex and fascinating task for the scientific community and the last decade has been full of new findings on how the disease starts and how it causes damage to different organ systems. However, we have still more questions than answers in this topic, answers that will be critical to understanding autoimmunity and finding effective therapies to dermatomyositis.

Variation at HLA-DPB1 is associated with dermatomyositis in Chinese population

Dermatomyositis (DM) is a polygenic disorder characterized by inflammation of skeletal muscle and skin. To date, the exact etiopathogenesis of DM remains elusive. To explore the genetic basis of DM, we conducted genome-wide genotyping analysis of 127 patients and 1566 healthy controls by Illumina Human OmniZhongHua-8 BeadChips in the Chinese Han population. We investigated whether the three SNP (rs7750458, rs9501251 and rs9500928) at 6p21.32 in the HLA-DPB1 gene were significantly associated with DM (P < 5 × 10^-8 ) and identified two susceptibility loci at 7q34 (PIP, rs9986765, P = 7.45 × 10^-7 , odds ratio [OR] = 2.71) and 10q24.2 (CPN1, rs3750716, P = 9.04 × 10^-7 , OR = 4.39) with suggestive evidence. We imputed 6674 classical human leukocyte antigen (HLA) alleles, amino acids and SNP from the discovery dataset, and stepwise analysis revealed that HLA-DPB1*17 in class II HLA genes were significantly associated with DM susceptibility. This study represents the first genome-wide association study (GWAS) of DM in the Chinese Han population. For the first time, HLA-DPB1 was found to be associated with DM in this population. Moreover, we identified two novel suggestive susceptibility loci (PIP and CPN1) and confirmed four previously reported genes (DMB, DQA1, DQB1 and DRB1) having potential associations with DM in the Chinese Han population. Our GWAS results in this population should provide important information regarding the genetic etiopathogenesis of DM and facilitate the development of new therapies for the treatment of DM and the prevention of DM progression.

Idiopathic inflammatory myopathies

Inflammatory myopathies are chronic, immune-mediated diseases characterised by progressive proximal muscle weakness. They encompass a variety of syndromes with protean manifestations. The diagnosis is based on Bohan and Peter's classification criteria, which nowadays seem to be obsolete. Our increasing knowledge about the risk factors, genetic susceptibility and immunological pathways in the disease mechanism leads to the establishment of a new, immunogenetically and serologically validated diagnostic criteria system. The treatment of idiopathic inflammatory myopathy is also a complex task requiring much experience. The aims of therapy are to increase muscle strength, prevent the development of contractures and manage the systemic manifestations of the disease. The most important one is the early detection of diseases and patients' immunological control in special centres. Using the basis therapeutic drugs temporary or permanent remission can be achieved, which improves patientsG' quality of life and functional ability. Rehabilitation and physiotherapy in the remission period may significantly improve the outcome of patients with functional disorders. The introduction of new biological therapies further allows us to control the myositis patients' state more effectively. The aim of this review is to summarise our knowledge about clinical symptoms, pathomechanism, as well as genetic, serologic and environmental risk factors. We would also like to present the way to diagnosis and the latest research about diagnostic criteria system, proposed outcome measures and therapeutic possibilities.

Marked improvement of calcinosis in adult dermatomyositis with etidronate therapy

We report a 26-year-old woman with severe calcinosis associated with dermatomyositis. Although calcinosis of the skin or muscles is unusual in adults with dermatomyositis, this patient developed subcutaneous calcinosis with tenderness on the arms, axillary areas, shoulder areas, chest, abdomen, pelvis, and limbs. The calcinosis steadily increased and spread until joint motions were severely limited. Radiographic examination showed extensive soft-tissue calcification with a reticular pattern and severe osteoporosis. The patient was treated with oral etidronate (800 mg/day for 3 months every 6 months) to prevent calcification of the lesions. Three months later, the patient showed a dramatic improvement in symptoms with softening of the calcinosis, reduced pain, and marked increase in joint mobility. Radiographic examination showed marked decreases in the size of the calcified lesions compared to pre-treatment findings, and this effect persisted with a constant progressive efficacy for 3 years. The 3-year course of etidronate therapy also resulted in marked improvement of the severe osteoporosis and the patient was able to return to work and enjoy a normal life. We propose etidronate as a beneficial and effective therapy for calcinosis with osteoporosis.

Interaction of HLA-DRB1*03 and smoking for the development of anti-Jo-1 antibodies in adult idiopathic inflammatory myopathies: a European-wide case study

Objectives

HLA-DRB1*03 is strongly associated with anti-Jo-1-positive idiopathic inflammatory myopathies (IIM) and there is now increasing evidence that Jo-1 antigen is preferentially expressed in lung tissue. This study examined whether smoking was associated with the development of anti-Jo-1 antibodies in HLA-DRB1*03-positive IIM.

Methods

IIM cases were selected with concurrent information regarding HLA-DRB1 status, smoking history and anti-Jo-1 antibody status. DNA was genotyped at DRB1 using a commercial sequence-specific oligonucleotide kit. Anti-Jo-1 antibody status was established using a line blot assay or immunoprecipitation.

Results

557 Caucasian IIM patients were recruited from Hungary (181), UK (99), Sweden (94) and Czech Republic (183). Smoking frequency was increased in anti-Jo-1-positive IIM cases, and reached statistical significance in Hungarian IIM (45% Jo-1-positive vs 17% Jo-1-negative, OR 3.94, 95% CI 1.53 to 9.89, p<0.0001). A strong association between HLA-DRB1*03 and anti-Jo-1 status was observed across all four cohorts (DRB1*03 frequency: 74% Jo-1-positive vs 35% Jo-1-negative, OR 5.55, 95% CI 3.42 to 9.14, p<0.0001). The frequency of HLA-DRB1*03 was increased in smokers. The frequency of anti-Jo-1 was increased in DRB1*03-positive smokers vs DRB1*03-negative non-smokers (42% vs 8%, OR 7.75, 95% CI 4.21 to 14.28, p<0.0001) and DRB1*03-positive non-smokers (42% vs 31%, p=0.08). In DRB1*03-negative patients, anti-Jo-1 status between smokers and non-smokers was not significantly different. No significant interaction was noted between smoking and DRB1*03 status using anti-Jo-1 as the outcome measure.

Conclusion

Smoking appears to be associated with an increased risk of possession of anti-Jo-1 in HLA-DRB1*03-positive IIM cases. The authors hypothesise that an interaction between HLA-DRB1*03 and smoking may prime the development of anti-Jo-1 antibodies.

Recent advances in the immunogenetics of idiopathic inflammatory myopathy

This review summarizes the previous and current literature on the immunogenetics of idiopathic inflammatory myopathy (IIM) and updates the research progress that has been made over the past decade. A substantial part of the genetic risk for developing adult- and juvenile-onset IIM lies within the major histocompatibility complex (MHC), and a tight relationship exists between individual human leukocyte antigen alleles and specific serological subtypes, which in turn dictate clinical disease phenotypes. Multiple genetic regions outside of the MHC are increasingly being identified in conferring IIM disease susceptibility. We are still challenged with the task of studying a serologically and clinically heterogeneous disorder that is rarer by orders of magnitude than the likes of rheumatoid arthritis. An ongoing and internationally coordinated IIM genome-wide association study may provide further insights into IIM immunogenetics.

[Pathogenesis of the idiopathic inflammatory myopathies]

The inflammatory myopathies, commonly described as idiopathic, are a group of acquired diseases characterized by an inflammatory infiltrate of the skeletal muscle. On the basis of clinical and immuno-pathological features, three major diseases can be identified: dermatomiositis (DM), polymyositis (PM) and inclusion body myositis (IBM). Immunopathogenesis mechanisms are crucial for discriminating between the three different subsets of inflammatory myopathies. DM is a complement-mediated microangiopathy affecting skin and muscle. PM and IBM are T cell-mediated disorders, where CD8-positive cytotoxic T cells invade muscle fibres expressing MHC class I antigens. This article summarizes the main immunopathological markers. The impact of this new knowledge must be defined in relation to potential therapeutic targets for idiopathic inflammatory myopathies.

Immunoglobulin gene polymorphisms are susceptibility factors in clinical and autoantibody subgroups of the idiopathic inflammatory myopathies

OBJECTIVE

To investigate possible associations of GM and KM markers with adult and juvenile forms of the idiopathic inflammatory myopathies (IIMs) in Caucasian and African American patients.

METHODS

We performed serologic analyses of polymorphic determinants associated with immunoglobulin gamma heavy chains (GM) and kappa light chains (KM) in large populations of Caucasian patients (n= 514 [297 adults and 217 children]) and African American patients (n=123 [73 adults and 50 children]) with IIM representing the major clinical and autoantibody groups.

RESULTS

For Caucasian patients with dermatomyositis (DM), the Gm 3 23 5,13 phenotype was a risk factor in both adults (odds ratio [OR] 2.2, corrected P [Pcorr]=0.020) and children (OR 2.2, Pcorr=0.0013). Of interest, the GM 13 allotype was a risk factor for juvenile DM in both Caucasian subjects (OR 3.9, Pcorr<0.0001) and African American subjects (OR 4.8, Pcorr=0.033). However, the Gm 1,3,17 5,13,21 phenotype was a risk factor for juvenile DM in Caucasian subjects but not African American subjects. Among the IIM autoantibody groups, Gm 3 23 5,13 was a risk factor in Caucasian adults with anti-Jo-1 autoantibodies (OR 3.4, Pcorr=0.0031), while the GM 3 allotype was protective in adults with anti-threonyl-transfer RNA synthetase or anti-U RNP autoantibodies (OR 0.1, Pcorr=0.047 and OR 0.2, Pcorr=0.034, respectively). In contrast, GM 6 was a risk factor in African American adults with anti-signal recognition particle autoantibodies (OR 7.5, Pcorr=0.041).

CONCLUSION

These data suggest that polymorphic alleles of GM and KM loci are differentially associated with IIM subgroups defined by age, ethnicity, clinical features, and autoantibody status, and expand the list of immune response genes that are possibly important in the pathogenesis of myositis.

Are pediatric autoimmune diseases primarily genetic diseases?

PURPOSE OF REVIEW

Powerful new methods are allowing identification of genetic risk factors in large populations of adults with autoimmune diseases. In this review, we describe the advantages and limitations of genetic methodologies, and how these methods have been used to discover candidate genes in smaller populations of pediatric patients. We also introduce novel concepts for nontraditional modes of genetic inheritance that may be important in the pathogenesis of autoimmunity.

RECENT FINDINGS

Candidate genes identified by linkage analyses and genome-wide association scans in adult populations have led to focused genetic studies in pediatric populations. Some genes are associated with subsets of both adult and pediatric patients; others appear to be age specific. Novel concepts in genetics have uncovered potential contributions of maternal compared with paternal transmission, noninherited maternal alleles that may work through maternal microchimerism, and sex-specific epigenetic mechanisms of immunoregulation.

SUMMARY

Advancing methods are leading to the discovery of genes associated with childhood autoimmune diseases. However, the genetic contribution to disease risk for any one gene remains less than 30% for most diseases, suggesting that pediatric autoimmunity is not primarily genetic in a classical sense. A combinatorial approach considering the contributions of multiple genes, mode of inheritance, and environmental influences will be required to fully understand the mechanisms of pathogenesis in pediatric autoimmune disease.

Immunogenetic risk and protective factors for juvenile dermatomyositis in Caucasians

OBJECTIVE

To define the relative importance (RI) of class II major histocompatibility complex (MHC) alleles and peptide binding motifs as risk or protective factors for juvenile dermatomyositis (DM), and to compare these with HLA associations in adult DM.

METHODS

DRB1 and DQA1 typing was performed in 142 Caucasian patients with juvenile DM, and the results were compared with HLA typing data from 193 patients with adult DM and 797 race-matched controls. Random Forests classification and multiple logistic regression were used to assess the RI of the HLA associations.

RESULTS

The HLA-DRB1*0301 allele was a primary risk factor (odds ratio [OR] 3.9), while DQA1*0301 (OR 2.8), DQA1*0501 (OR 2.1), and homozygosity for DQA1*0501 (OR 3.2) were additional risk factors for juvenile DM. These risk factors were not present in patients with adult DM without defined autoantibodies. DQA1 alleles *0201 (OR 0.37), *0101 (OR 0.38), and *0102 (OR 0.51) were identified as novel protective factors for juvenile DM, the latter 2 also being protective factors in adult DM. The peptide binding motif DRB1 (9)EYSTS(13) was a risk factor, and DQA1 motifs F(25), S(26), and (45)(V/A)W(R/K)(47) were protective. Random Forests classification analysis revealed that among the identified risk factors for juvenile DM, DRB1*0301 had a higher RI (100%) than DQA1*0301 (RI 57%), DQA1*0501 (RI 42%), or the peptide binding motifs. In a logistic regression model, DRB1*0301 and DQA1*0201 were the strongest risk and protective factors, respectively, for juvenile DM.

CONCLUSION

DRB1*0301 is ranked higher in RI than DQA1*0501 as a risk factor for juvenile DM. DQA1*0301 is a newly identified HLA risk factor for juvenile DM, while 3 of the DQA1 alleles studied are newly identified protective factors for juvenile DM.

Atteinte pulmonaire au cours des polymyosites et des dermatomyosites

Interstitial lung disease is a serious complication of polymyositis/dermatomyositis and leads to death from chronic respiratory insufficiency in 30 to 66% of cases. It is a criterion of poor prognosis in these disorders. Its onset occurs at variable points in the course of polymyositis/dermatomyositis, and precedes them in half of all cases. Presentation may also vary: acute (25%), insidious (60%), or infraclinical, discovered fortuitously (15%). The examinations of choice for early screening are high-resolution computed tomography (CT) and pulmonary function tests, which should be performed during the initial work-up and during ongoing surveillance. Moreover, high-resolution CT also makes it possible to determine the type of histologic lesions in the interstitial lung disease. Today, diagnosis of this disease does not generally require histological confirmation; nonspecific interstitial lung disease seems to be the most common histologic form of lung damage in polymyositis/dermatomyositis (40 to 80%). Anti-Jo1 antibodies are a sensitive marker of interstitial lung disease during polymyositis/dermatomyositis, and close surveillance of lung function is recommended in patients with these autoantibodies. Systematic testing for them is also justified in patients with apparently idiopathic interstitial lung disease, to rule out underlying polymyositis/dermatomyositis. No clear treatment protocols have been established for interstitial lung disease during polymyositis/dermatomyositis. Corticosteroid treatment is the first choice. Its combination with cyclophosphamide may be most effective in corticosteroid-resistant forms of polymyositis/dermatomyositis, especially when begun early; it may also be appropriate to begin corticosteroids as soon as factors predicting poor prognosis are detected.

Have recent immunogenetic investigations increased our understanding of disease mechanisms in the idiopathic inflammatory myopathies?

PURPOSE OF REVIEW

The idiopathic inflammatory myopathies (IIM) continue to provide a challenge given the variable effectiveness of the available treatments, and immunogenetic studies are ongoing to further elucidate IIM disease mechanisms. This review examines how recent research has improved our understanding of the mechanisms that lead to IIM.

RECENT FINDINGS

HLA-DRB1 studies in a large homogenous cohort of UK Caucasian patients have confirmed that polymyositis (PM) and dermatomyositis (DM) are not genetically identical diseases while other studies have shown that tumor necrosis factor alpha is genetically implicated in disease susceptibility. Some remarkable results from an international collaboration, correlating gene-environment interactions, clearly suggest that ultraviolet light is capable of modulating both clinical and immunologic features of IIMs. Studies on microchimerism are unraveling interesting associations in juvenile DM patients, and bolstering the hypothesis that myositis may be an 'allo-immune' disease. mRNA gene expression profiling is helping to increase our understanding of myositis pathogenesis, whilst animal models have provided new information on the roles of Th1 responses and nitric oxide synthase in muscle disease. New candidate genes have been examined in inclusion body myositis (IBM), and a novel gene transfer experiment has been conducted, which led to significant changes in expression of the IBM phenotype.

SUMMARY

Improving the understanding of the immunogenetics and immunopathogenesis of the IIMs may in the future provide novel therapeutic targets, and thus improve outcomes in these difficult diseases.

Cytokines in juvenile dermatomyositis pathophysiology: potential and challenge

PURPOSE OF REVIEW

Cytokines are criticalmediators of the immune response. This review focuses on cytokine-specific information from children with juvenile dermatomyositis, and includes pertinent data from adults with polymyositis and dermatomyositis.

RECENT FINDINGS

Much of the new data concern the role of possible antigens and the definition of genetic control of the immune response in juvenile dermatomyositis. Gene expression profile data of DQA1*0501 (present in 85% of patients) compared with age-matched control subjects show that the initial immune response is an interferon-alpha/beta-induced cascade with secondary stimulation of interferon-gamma. Specific epitopes of group A beta-hemolytic streptococcal M protein, with sequence homology for myosin, elicit both cell-mediated cytotoxicity and tumor necrosis factor-alpha production when incubated with mononuclear cells from children with active juvenile dermatomyositis. Tumor necrosis factor-alpha synthesis is increased in juvenile dermatomyositis patients with the tumor necrosis factor-alpha-308A allele, and is associated with increased thrombospondin-1 (an antiangiogenic agent) production and small vessel occlusion in untreated juvenile dermatomyositis. Studies in adults with polymyositis and dermatomyositis implicate interleukin-1alpha, transforming growth factor-beta, and endothelial cell perturbation early in the disease course. Cultured myoblasts were found to produce interleukin-15, which impacts local T-cell activation and proliferation.

SUMMARY

The limited data suggest that a possible viral/microbial antigen may elicit an interferon-alpha/beta-induced response, and that antigenic epitopes may be shared. Increased synthesis of tumor necrosis factor-alpha, more common in juvenile dermatomyositis with the tumor necrosis factor-alpha-308A polymorphism, may augment this response and is associated with a wide range of pathologic consequences, as well as disease chronicity and calcifications. The muscle fibers themselves can regulate local inflammation by production of tumor necrosis factor-alpha, interleukin-15 and interleukin-1alpha, and transforming growth factor-beta.

Inclusion body myositis: clonal expansions of muscle-infiltrating T cells persist over time

Inclusion body myositis (IBM) is a chronic inflammatory myopathy. The muscle histology is characterized by infiltration of T cells, which invade and apparently destroy muscle fibres. This study was performed to investigate whether predominant clones of muscle-infiltrating T cells are identical in different muscles and whether they persist over time in IBM. By reverse transcriptase-polymerase chain reaction, 25 T-cell receptor (TCR) variable beta (Vbeta) chain families and the complementarity-determining region 3 (CDR3) of the TCR were analysed in two different muscle biopsies of four patients with IBM. In two of the patients, the muscle biopsies were obtained from different muscles at one time point, whereas in two patients, the second biopsy was obtained 9 years after the first biopsy. T cells expressing predominant Vbeta families were analysed for clonality by fragment length analysis of the CDR3. Predominant Vbeta families were analysed by DNA sequencing to identify identical clones. Immunohistochemical staining of Vbeta families was performed to study the distribution of T cells expressing identified predominant Vbeta families. The muscle-infiltrating lymphocytes showed restricted expression of TCR Vbeta families. DNA sequencing proved that clonally expanded T cells were identical in different muscles and persisted 9 years after the first biopsy. Immunohistochemical analysis with Vbeta family-specific antibodies demonstrated the endomysial localization of these T cells in inflammatory cell infiltrates. Our results show that in IBM there is clonal restriction of TCR expression in muscle-infiltrating lymphocytes. Identical T-cell clones predominate in different muscles, and these clones persist for many years. These results indicate an important, continuous, antigen-driven inflammatory reaction in IBM.

Genetic and environmental risk factors for idiopathic inflammatory myopathies

Although the studies discussed are beginning to reveal a number of genetic and possible environmental risk factors for myositis, further investigations are needed to fully understand and classify these syndromes. The difficulties in this process include small numbers of subjects with varying disease phenotypes available for study, polygenic risk factors for which it remains unclear which are primary and which are secondary or linked genes, and the lack of validated environmental exposure assessment tools. New technologies and international collaborative approaches, however, may overcome some of these difficulties and allow us to identify genetic and environmental risk factors, as well as the critical gene-environment interactions in the IIM and its subgroups. Nonetheless, our understanding of these diseases is still in the early stages. Although we have learned a great deal about these disorders through detailed investigations over the last several decades, we have even further to go to understand the environmental triggers and genetic susceptibilities for the myositis syndromes.

Polymyositis: clinical investigation in two sisters

We present an investigation of a case of polymyositis affecting two sisters of one same parenthood. Their cases have been documented for almost two decades, being investigated by means of a diagnostic protocol which combined clinical findings as well as laboratorial, histopathological and image tests. In both cases, clinical manifestations started in childhood, without signs of involvement of the central and peripheral nervous system. Both patients proved to respond to a therapeutics based on corticosteroids. The degree of relatedness between their parents corroborate the notion that genetic factors may contribute to the development of the disease.

Dermatomyositis: an overview of recent progress with emphasis on dermatologic aspects

Important points regarding DM and C-ADM are as follows: C-ADM is a working functional designation for patients having the skin-only and skin-predominant subsets of DM, amyopathic DM, and hypomyopathic DM. C-ADM seems to have approximately 10% the incidence of classic DM in whites and possibly a higher incidence in Asians. Some patients who present with C-ADM, with or without subclinical laboratory abnormalities, can slowly progress to develop symptomatic muscle weakness over a period of years, whereas others go for 10 to 20 years and longer without the appearance of muscle weakness. C-ADM patients are at risk for potentially life-threatening complications of classic DM, such as interstitial lung disease, which may occur in up to 10% of C-ADM patients. This risk seems to be even greater in some ethnic subgroups (e.g., Japanese). C-ADM patients may also be at increased risk for internal malignancy and until further studies are carried out to confirm the statistical significance of this association, all such patients should have a thorough evaluation for internal malignancy, identical to the approach currently used in classic DM patients. Dermatologists are in the best position initially to diagnose C-ADM patients and can contribute greatly to their overall management and quality of life. Ongoing vigilance is required, however, for complications that can arise in C-ADM patients including potentially fatal interstitial lung disease, internal malignancy, delayed onset of muscle weakness from myositis, and complications of systemic drug therapy. Topical therapy with broad-spectrum sunscreens, anti-inflammatories, and antipruritics should be maximized during the initial management of the cutaneous manifestations of either classic DM or C-ADM. Single-agent or combined aminoquinoline antimalarial therapy represents the safest initial form of systemic therapy for DM-specific skin disease occurring in any clinical setting; however, this approach tends to be less effective in general than for cutaneous LE. There is a theoretical rationale for and limited preliminary successful anecdotal experience with the use of anti-TNF-alpha therapy in refractory cases of classic DM and C-ADM. Cautious systematic clinical trials in this area should be considered.

Dermatomyositis in two siblings and a brief review of familial dermatomyositis

Juvenile dermatomyositis is an uncommon autoimmune disease with classic heliotrope discoloration of the eyelids, erythematous skin rash of joints, and proximal muscle weakness. It is most frequently sporadic and only rarely familial. We present juvenile dermatomyositis in a 5-year-old brother and a 3 1/2-year-old sister, both are very responsive to corticosteroids. Familial dermatomyositis can occur in different family members, and even dermatomyositis and polymyositis can coexist in the same family.

Gene expression profiling in DQA1*0501+ children with untreated dermatomyositis: a novel model of pathogenesis

Juvenile dermatomyositis (JDM), the most common pediatric inflammatory myopathy, is a systemic vasculopathy affecting young children. Epidemiology studies documenting an antecedent illness in the 3 mo before the first definite symptom (rash and/or weakness) of JDM are supported by immunologic data that suggest that the disease pathophysiology is Ag driven. The purpose of this study was to compare the gene expression profiles in muscle biopsies of four untreated DQA1*0501(+) JDM children with profiles from children with a known necrotizing myopathy (Duchenne muscular dystrophy), as well as an in vitro antiviral model (NF90), and healthy pediatric controls. Nearly half (47%) of the dysregulated genes in JDM were associated with the immune response. In particular, increased expression of IFN-alphabeta-inducible genes 6-16, myxovirus resistance protein p78, latent cytosolic transcription factor, LMP2, and TAP1 was observed. This profile is consistent with an IFN-alphabeta transcription cascade seen in the in vitro viral resistance model. The IFN-alphabeta-inducible profile was superimposed on transcription profiles reflective of myofiber necrosis and regeneration shared with Duchenne muscular dystrophy. Expressed genes were confirmed by quantitative real-time PCR (6-16), immunofluorescence (thrombospondin 4), and immunolocalization (IFN-gamma, p21). We hypothesize that these data support a model of Ag (?viral) induction of an apparent autoimmune disease based on dynamic interaction between the muscle, vascular, and immune systems in the genetically susceptible (DQA1*0501(+)) child.

Transglutaminases in disease

Transglutaminases (TGases) are enzymes that are widely used in many biological systems for generic tissue stabilization purposes. Mutations resulting in lost activity underlie several serious disorders. In addition, new evidence documents that they may also be aberrantly activated in tissues and cells and contribute to a variety of diseases, including neurodegenerative diseases such as Alzheimer's and Huntington's diseases. In these cases, the TGases appear to be a factor in the formation of inappropriate proteinaceous aggregates that may be cytotoxic. In other cases such as celiac disease, however, TGases are involved in the generation of autoantibodies. Further, in diseases such as progressive supranuclear palsy, Huntington's, Alzheimer's and Parkinson's diseases, the aberrant activation of TGases may be caused by oxidative stress and inflammation. This review will examine the role and activation of TGases in a variety of diseases.

[Interstitial lung diseases in polymyositis and dermatomyositis]

PURPOSE

Interstitial lung disease is one of the most common respiratory manifestations in polymyositis and dermatomyositis. It still remains a severe complication of the disease, leading to death related to ventilatory insufficiency in 30-66% of patients.

CURRENT KNOWLEDGE AND KEY POINTS

Time onset of interstitial lung disease is variable, although interstitial lung disease onset precedes initial manifestations of polymyositis/dermatomyositis in roughly half of the patients. Moreover, clinical presentation of interstitial lung disease can be dichotomized, according to patients' pulmonary manifestations, into: 1) both acute and aggressive lung disease similar to Hamman-Rich syndrome; 2) slowly progressive lung disease; and 3) an asymptomatic pattern. The methods of choice adopted for early diagnosis of interstitial lung disease are high-resolution computed tomography scan and pulmonary function tests, which should be performed during both initial evaluation of polymyositis/dermatomyositis and follow-up. Because anti-JO1 antibody is considered to be a marker of interstitial lung disease in polymyositis/dermatomyositis, close pulmonary follow-up of anti-JO1-positive patients with polymyositis is therefore required for early detection of subclinical impairment. Furthermore, histological lung findings provide prognostic data; patients with bronchiolitis obliterans organizing pneumonia (BOOP) indeed appear to have a more favorable outcome than those with usual interstitial pneumonia or diffuse alveolar damage. Finally, as a guide to both the severity and progress of interstitial lung disease, the significance of other investigations, notably bronchoalveolar lavage, remains controversial.

FUTURE PROSPECTS AND PROJECTS

Specific therapy of interstitial lung disease has not yet been clearly established in polymyositis/dermatomyositis patients. Corticosteroid therapy is considered the first line of therapy for polymyositis/dermatomyositis patients with interstitial lung disease. The association of cyclophosphamide and corticosteroids may be the most effective in patients with steroid-resistant interstitial lung disease. Early diagnosis and management of this disease is therefore of the utmost importance.

Juvenile dermatomyositis: the association of the TNF alpha-308A allele and disease chronicity

Little is known concerning factors associated with the outcome of juvenile dermatomyositis (JDM), which can be variable and lethal. Previous work has documented that the association of DQA1*0501 with JDM is higher than in control groups and that the first symptoms (rash and weakness) of JDM appear to follow evidence of an infectious process--most frequently upper respiratory in nature. Preliminary data show that a long period of symptoms being left untreated before starting therapy and the TNF alpha-308A allele are associated with prolonged JDM symptoms requiring > or = 36 months of immunosuppressive therapy. A short duration of untreated disease is associated with a relative increase in CD8(+) T cells and CD56(+) natural killer (NK) cells in the untreated JDM muscle biopsy compared with a longer duration of untreated disease. The TNF alpha-308A allele is overrepresented in white children with JDM. In addition, it is associated with pathologic calcifications, increased production of TNF alpha by peripheral blood mononuclear cells in vitro and JDM muscle fibers in vivo, and occlusion of capillaries, which may be mediated in part by elevated circulating levels of thrombospondin-1, a potent anti-angiogenic factor. We speculate that DQA1*0501 is associated with JDM susceptibility to an infectious process, eliciting and activating NK cells early in the disease course. We conclude that the TNF alpha-308A allele indicates directly (or is a surrogate marker of) children with JDM who produce higher concentrations of TNF alpha in response to this undefined inflammatory stimulus, as well as increased concentrations of TSP-1 with resultant small vessel occlusion, contributing to subsequent disease chronicity.

Dermatomyositis

Dermatomyositis is a disease that has a characteristic skin eruption that may occur with or without a proximal myopathy. The disease with cutaneous features only is classified as amyopathic dermatomyositis. The origin is unknown, but autoimmune factors are believed to play an important role. Autoantibodies are found in most patients and some have myositis-specific antibodies. Systemic changes may occur and there appears to be a relationship to internal malignancy, particularly in older patients. Juvenile disease has an associated vasculopathy. Treatment includes systemic corticosteroids and other immunosuppressive agents. The cutaneous changes may be difficult to treat.

Update on the genetics of the idiopathic inflammatory myopathies

A number of lines of investigation suggest that, as is likely the case for other autoimmune diseases, the idiopathic inflammatory myopathies (IIM) develop as a result of specific environmental exposures in genetically susceptible individuals. Current data imply that multiple genes are involved in the etiology of these complex disorders. Targeted gene studies and whole genome approaches have begun to identify several genetic risk factors for autoimmune diseases, but the rarity and heterogeneity of the IIM have limited our knowledge of their associated genes. Current findings suggest that human leukocyte antigen (HLA) genes on chromosome 6, particularly HLA DRB1*0301 and the linked allele DQA1*0501, have the strongest associations with all clinical forms of IIM in white patients. Different HLA alleles, however, may confer risk or protection for myositis in distinct ethnic, serologic, and environmental exposure groups. Non-HLA genetic risk factors, which have been documented for other autoimmune diseases, are now being identified for the IIM. These include polymorphic genes encoding immunoglobulin heavy chains (defined by serologic markers known as Gm allotypes), cytokines and their receptors, and certain proteins that accumulate in the myocyte vacuoles of inclusion body myositis patients. Selected allelic polymorphisms of interleukin-1 receptor antagonist variable number tandem repeats and genes for tumor necrosis factor alpha and interleukin-1 alpha also have recently been associated with IIM. The pathogenic bases for the differences among the many clinically, pathologically and immunologically defined syndromes known as the IIM will be elucidated through a better understanding of the multiple genes that define risks for their development, as well as through investigations of gene-gene and gene-environment interactions.

Inflammatory myositis in children, including differential diagnosis

Advances in dermatomyositis and the juvenile idiopathic inflammatory myopathies over the past year included the development of new possible disease activity markers. Further evidence that these markers correlate with disease activity will give clinicians tools necessary for assessment of patient response to therapy. Validated disease activity and outcome measures will also allow for assessment of efficacy of new therapies as well as new combinations of older therapies. Basic questions about risks and benefits of widely used therapies such as pulse intravenous methylprednisolone still need to be addressed. Some open-label and retrospective assessments of therapeutic strategies for idiopathic inflammatory myopathies were recently published. Finally, further delineation of the roles of genetics, environment and immunity in the pathogenesis and course of the juvenile idiopathic inflammatory myopathies continued this year.

Familial autoimmunity and the idiopathic inflammatory myopathies

Many lines of evidence suggest that autoimmune diseases result from chronic immune activation following environmental exposures in genetically susceptible individuals. A genetic basis for autoimmunity is supported by twin and family studies, candidate gene investigations, animal models, and whole genome microsatellite scans. These findings predict, and clinical observations support, familial clustering of a number of individual autoimmune diseases, notably lupus, multiple sclerosis, type-1 diabetes mellitus, rheumatoid arthritis, and recently the idiopathic inflammatory myopathies. Yet, not only is the same autoimmune disease increased in prevalence in pedigrees of persons affected with a given disorder, but other autoimmune diseases are as well. We review these data and propose a hypothesis consistent with these findings. This model posits that a rheumatic disease, as currently classified, is actually composed of a number of elemental disorders. Each of these is defined by the minimal necessary and sufficient environmental exposures and genes that result in a pathology leading to a given sign-symptom complex.

Immunogenetic associations in childhood dermatomyositis

Childhood dermatomyositis is a multisystem autoimmune disease characterized by acute and chronic inflammatory infiltrate and vasculitis seen primarily in skin and muscle. The disease occurs in genetically susceptible individuals with a yet undescribed environmental trigger. Genetic associations in this disease demonstrate disease susceptibility as well as chronicity and severity and likely play a role in disease pathogenesis. The majority of the associations to date have been seen with the HLA alleles, with additional immune responsive and influential genes being increasingly investigated.

Inclusion body myositis

Sporadic inclusion body myositis is a severely disabling muscle disease that mainly affects elderly individuals. The typical distribution of muscle weakness, poor response to immunosuppressive treatment, pathological accumulation of various proteins in vacuolated muscle fibres, inflammatory reaction and mitochondrial changes have all been subjects of recent research that has led to better understanding of the pathogenic events that leads to muscle degeneration and weakness.